1. Field Of The Invention
This invention relates generally to the field of electrode arrangements and, more particularly, to the field of electrode arrangements useful for EEG and ECG systems.
2. Description Of The Prior Art
Various electrode arrangements have been developed for electrocardiogram systems which produce electrocardiograms that are accurately representative of the heart beat of a person or animal. Two such electrode arrangements are disclosed in a U.S. Pat. No. 3,841,312 to Corasanti, the inventor of the device herein described and No. 3,845,757 to Weyer. Electrodes of the type disclosed in the Corasanti patent detect electric potentials or voltages generated by a body and are electrically connected to measuring instruments where the voltages are recorded.
The body generates a minimum, relatively constant voltage, called the base line voltage, and variable wave form types of voltages, associated for example with heart beats and brain waves, superimposed on the base line voltage. A disadvantage associated with prior art electrode arrangements is that after a base line voltage is established on the measuring instruments of the EEG or ECG system, pressure or force on the electrode itself tends to cause an otherwise constant amplitude base line voltage to oscillate as a low frequency wave form. Consequently, the base line appears to shift from its original steady state amplitude. These shifts of the base line can tend to obscure the wave forms of the heart beat signal. A U.S. Pat. No. 3,518,984, issued to Mason, notes and explains in some detail the problem of baseline shift. Consequently, a need exists for a reliable, low cost, disposable electrode arrangement that can maintain a good electrical contact despite the placement of pressure or force upon the electrode.
A further disadvantage of prior art electrodes is that a sharp, instantaneous force on the electrode produces voltage wave forms which are similar to and can be mistaken for the variable, high frequency wave form types of voltages associated with, for example, heart beats.
Another disadvantage of prior art electrodes is that they are too rigid and not adaptable for placement on non-planar areas of the adult body or on limited surface areas presented by, for example, a premature or infant body.
Another disadvantage of prior art devices is that they can not be removed from their package prior to use. The usefulness of existing electrodes in emergency situations could be substantially improved if existing electrodes could be removed from their packages and attached to the EEG system prior to the emergency situation. However, existing electrodes can not be removed from their packages for long periods before being used without the dehydration of the gel member and thus without greatly affecting the nature of the electrical contact.